Overlapping Energy Range Research Articles

Observations of energetic neutral oxygen by IMAGE/HENA and Geotail/EPIC

Energetic neutral oxygen emissions from two satellites, IMAGE and Geotail, are examined during a magnetic storm interval on 2001 November 24–25. These two satellite observations provide different viewing perspectives of the energetic neutral emissions from the Earth's magnetosphere. IMAGE has a high inclination orbit while Geotail has a low one. Overlapping energy range of energetic neutral oxygen occurs for HENA on IMAGE and EPIC on Geotail. Quantitative comparison of oxygen energy spectra during this storm period indicates that viewing perspective plays an important role in the total intensity measured. This study constitutes the first quantitative inter‐spacecraft comparison of energetic neutral oxygen intensity.

First comparisons of local ion measurements in the inner magnetosphere with energetic neutral atom magnetospheric image inversions: Cluster‐CIS and IMAGE‐HENA observations

Data provided by the CIS (Cluster Ion Spectrometry) instruments on board the Cluster spacecraft are used to survey recent crossings of the inner magnetosphere and ring current. CIS is capable of obtaining full three‐dimensional ion distributions (about 0 to 40 keV/q) with one spacecraft spin time resolution and with mass‐per‐charge composition determination. Events are selected for which the Cluster spacecraft are within the field of view of the HENA (high‐energy neutral atom) imager on board IMAGE. HENA provides energetic neutral atom images with a high geometric factor and with a 120° × 360° field of view over the spin. The H+ ion distribution functions obtained in situ by CIS are then compared to the ones deduced by inverting the HENA hydrogen neutral atom images for the overlapping energy range of the two instruments (27–39 keV). This analysis concerns events obtained both during well‐developed ring current conditions (e.g., 18 April 2002 event) and during quiet magnetospheric conditions (e.g., 9 August 2001 event). The results show the consistency between the ion fluxes deduced from energetic neutral atom (ENA) image inversions and the fluxes measured locally. They thus show the complementarity of the two approaches. The locally measured fluxes provide the “ground truth,” and they give the detailed ion distributions. ENA images allow to situate local measurements into a global context and to position them with respect to the ring current large‐scale structure. Our results also show the limitations of the ion fluxes deduced from the ENA image inversions for images taken from a single vantage point, with a substantial scatter of the inversion fluxes with respect to the in situ measured ones and a more limited dynamic range.

Charge Transfer Interactions of N-(4-Carboxyphenyl)trimellitimide Dibutyl Ester

Charge transfer (CT) interactions of the dibutyl ester of N-(4-carboxyphenyl)trimellitimide (NCTD) dissolved in organic solvents have been investigated by means of UV absorption and fluorescence spectroscopy and time-resolved fluorescence measurements. The spectroscopic data are interpreted in connection with quantum mechanical calculations using the AM1 and ZINDO/S method. The electronic transition lowest in energy, observed as an absorption tail in the UV spectra, is interpreted as a direct intramolecular CT excitation from the N-(4-carboxyphenyl) moiety (donor) to the trimellit moiety (acceptor). Independent of the excitation wavelength, a dominant red-shifted CT emission is observed in the fluorescence spectra. Thus, in addition to the direct CT excitation, indirect methods of CT formation exist. In concentrated solutions ground-state stable dimer formation is observed. Direct monomeric CT excitation and ground-state stable dimer excitation takes place in an overlapping energy range. The ground-state ...

Determination of the inelastic mean free path (IMFP) of electrons in germanium and silicon by elastic peak electron spectroscopy (EPES) using an analyser of high resolution

The IMFP of electrons is a fundamental material parameter of surface analysis by AES, XPS, EPES and EELS. In surface analysis calculated IMFP values are used. Their experimental determination is rather difficult. The IMFP of amorphous Ge and polycrystalline Si was determined by comparing the elastic peak intensity ratios with electrolytic Ni reference sample of 1 nm surface roughness, achieved by dedicated Ar + ion bombardment cleaning and examined by STM. Experimental results obtained with a hemispherical analyser type ESA 31 developed by ATOMKI Debrecen have been evaluated by Monte Carlo analysis, based on Jablonski's differential elastic scattering cross sections and elaborated for the HSA analyser angular window. Due to the 5 × 10 −5 energy resolution of the ESA 31 no spectrometer correction was needed. The ratio of the background to the elastic peak was < 1% at 4 keV. The energy range was extended to 5keV using Ashley's IMFP data. Reasonable agreement was found with our previous CMA experimental results in the overlapping energy range and with Ashley. They exhibit systematically higher values by 15–20%. EPES proved to be an efficient tool for IMFP measurements.

Reaction rate of8Li(d, t)7Li

The astrophysical S(E) factor of8Li(d,t)7Li has been deduced from available data of the inverse reaction7Li(t,d)8 Li and is consistent with data of direct measurements in the overlapping energy range. The deduced reaction rate at T9=1 is about an order of magnitude higher than assumed previously.

Absolute total cross section measurements for intermediate-energy electron scattering. IV. Kr and Xe

For pt.III, see ibid., vol.20, no.19, p.5157-64 (1987). Absolute total cross section measurements with an overall experimental uncertainty below 5% were performed for Kr and Xe in the energy range from 80 eV to 4000 eV. The Xe measurements above 750 eV are the first available in the literature . In the overlapping energy range the present data are in good agreement with other experimental and semi-empirical results. Comparing the total cross sections for all noble gases it has been found that their energy dependencies do not follow the Born approximation even at the highest measured energies.

Comparison of the solar cosmic ray events on May 7, 1978, and November 22, 1977

An analysis has been made of the solar cosmic ray events on May 7, 1978, and November 22, 1977, to determine the energy spectra of the solar protons from 50 MeV to 10 GeV, the pitch angle distributions, the intensity‐time profiles, and the anisotropy‐time profiles. Data from neutron monitors and IMP 7 and 8 satellites were used. It is found that the energy spectra of the solar protons obtained from neutron monitors and satellite observations are in good agreement in the overlapping energy range when the pitch angle distribution is taken into account. The energy spectra covering three decades of energy and eight decades of intensity and their time variations were remarkably similar for the two events. The difference in the neutron monitor responses for the events was mainly due to the different pitch angle distributions. For the prompt particle event on May 7, 1978, the shapes of the intensity‐time profiles for various energies are the result of the energy dependence of the time‐extended injection of particles into the interplanetary medium. This event is especially important for the study of the acceleration of solar particles and their subsequent injection into the interplanetary medium. For the November 22, 1977, event, even though the propagation of the solar protons in the IMF was essentially diffusive, the solar particle injection was also observed to be time extended and energy dependent.

Electron removal from atomic hydrogen by collisions with fully stripped carbon

Total cross sections for charge transfer and impact ionization in ${\mathrm{C}}^{+6}$-H collisions have been calculated for the range of relative velocities (0.1-10) \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ cm/sec. At the lower velocities [(0.1-2) \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ cm/sec] coupled-state calculations in an impact-parameter approximation were made of the charge-transfer cross sections using a basis set of exact one-electron two-center wave functions. An investigation of the origin dependence of these perturbed stationary-state calculations showed that differences of about 30% in the cross sections occur when the origin is shifted from the target to the ion center. At the higher velocities a classical-trajectory Monte Carlo approach was employed to determine both the charge-transfer and impact-ionization cross sections. The two sets of calculations are in reasonable agreement in the overlapping energy range, and give a comprehensive picture of the overall electron-removal cross section. They show that electron capture dominates in the region between 0.1 \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ and 3 \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ cm/sec with a peak cross section of \ensuremath{\sim} 5 \ifmmode\times\else\texttimes\fi{} ${10}^{15}$ ${\mathrm{cm}}^{2}$ at $v\ensuremath{\approx}7\ifmmode\times\else\texttimes\fi{}{10}^{7}$ cm/sec. The capture is predominantly into the $n=4$ levels of the product ${\mathrm{C}}^{+5}$ ion. Impact ionization is found to be the most important electron removal process at velocities above 4 \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ cm/sec.

Neutron-Induced Fission Cross Section ofNp237

The neutron-induced fission cross section of Np/sup 237/ was measured as a function of neutron energy in the range 0.9 to 8.0 Mev. Measurements above 1.7 Mev were made relative to the fission cross section of U/sup 238/ using 2 pi / sup -/ counting of fission fragmnents from thin fissile deposits placed back to back in a gridded ionization chamber. In the range 0.9 to 2.8 Mev the energy dependence of the Np/sup 237/ fission cross section was determined relative to the T(p,n)He/sup 3/ yield, and the results were normalized to those of the comparison counting experiment in the overlapping energy range. Results show that the cross sectlon Increases above threshold to a maximum value of 1.75 barns at -2 Mev, decreases to 1.40 barns at approximately 5 Mev, and increases again to 2.14 barns at 8 Mev. Estimated uncertainty in the absolute magnitude of sigma f(Np) is plus or minus 7%. (auth)